With modern-day testing, Usyk. Even back then, I can't see Usyk losing to Moorer or even Bowe. Certainly not Ruiz. So I pick Uysk.
Holyfield, this is based on @NoChin ’s opinion of Daniel Dubois (https://www.boxingforum24.com/threads/dubois-beat-an-overrated-over-the-hill-wardley.749295/) because how did Usyk’s best win at heavyweight (Fury lost to an MMA fighter and AJ post-Ruiz bum) come against a low-level opponent, like Dubois, when Holyfield fought and beat HOF fighters as an actual cruiserweight (190-pounder)? It’s almost like Usyk doesn’t have a better heavyweight win than Tyson, Bowe, and Foreman. It’s also crazy that Holyfield became the oldest heavyweight champion when he fought Valuev. In all seriousness, Usyk would have a chance, but why are Usyk fans so quick to diminish his best wins? Also, I stand by the cruiserweight comment: if you are 200 pounds, you are not a cruiserweight. No one is convincing me. Jai Opetaia isn’t a heavyweight only in name. Also, it would be a close fight where I see Holyfield winning.